1. Field of the Invention
The present invention relates to a presentation system for making a presentation in a lecture, or the like, while pointing to an image displayed on a screen using a laser pointer. More particularly, the present invention relates to a system which enables mouse operation on the screen of a personal computer using a laser pointer, and also relates to a system which enables preventing discharge of laser beam against human body.
2. Description of the Related Art
When making a presentation in a lecture or the like using a liquid crystal projector, a laser pointer which projects a laser beam onto a screen and indicates a point of interest on the screen is often used. In recent years, presentations are often performed while projecting images on a display of a personal computer onto a screen by using a liquid crystal projector or the like. In these cases, a mouse, which is one of the input devices for the personal computer, is operated. In recent years, a system in which light such as infrared light is irradiated onto a screen instead of a laser pointer dangerous for eyes, the irradiated spot is picked up by image pickup device to operate the coordinate, and a point image is projected to the operated coordinate is suggested. Such pointing systems are disclosed in Japanese Patent No. 2622620, No. 2977559, Japanese Unexamined Patent Application Publication No. 85395/99, and No. 143636/99, and are well known.
Although the mouse is usually operated by the presenter and the mouse is connected to the personal computer, the mouse operation can be applied to the pointing system which are disclosed in the Publication mentioned above. However, in these past techniques, position of an irradiated spot of infrared light or the like on the screen can be picked up as an only one coordinate on the pickup picture. That is, because an absolute position of projected spot of infrared light is operated as a coordinate to project a point image to a screen according to the operated result, physical relationship between the image pickup device and the screen must be rigorously decided from the optical viewpoint to organize the system. That is to say, a screen image which is picked up by the image pickup device can be easily distorted into trapezoid shape due to a difference of distances, and several corrections are required to settle a coordinate on the screen. Therefore, it is supposed that optical device and electrical system or system soft may become complicated.